If you’re looking for info on paper sizes, how they compare in the USA vs the UK, and what their measurements are then read our ultimate guide below.

Paper sizes differ depending on whether you live in the USA, Canada, the United Kingdom or Europe. This is largely due to the different systems of measurement in place, with the USA using imperial measurements (inches and feet) and most of the rest of the world using the metric system (millimetres and centimetres).

In our guide below we show different paper sizes/dimensions, and how they compare to each other.


USA Paper Sizes

View information on USA paper sizes

UK / International Paper Sizes

View information on International paper sizes


What are the UK / International Paper sizes?

There are 11 standard UK paper sizes, belonging to the A-class. Sizes start with the largest size A0 to the smallest size A10.

UK paper sizes follow the ISO 216 (International Organisation for Standardisation) size, which is the most commonly used paper size / standard across the world.

As paper sizes get smaller, you can work out the next size down by dividing the longest side by 2. For example, for an A3 sheet of paper measuring 297 mm x 420 mm, the next size down is an A4 sheet. Dividing the longest side 420 mm by 2 gives us 210 mm. An A4 sheet measures 210 mm x 297 mm.

UK Paper sizes chart

Paper Class












Size in mm

841 x 1189 mm

594 x 841 mm

420 x 594 mm

297 x 420 mm

210 x 297 mm

148.5 x 210 mm

105 x 148.5 mm

74 x 105 mm

52 x 74 mm

37 x 52 mm

26 x 37 mm

Size in cm

84.1 x 118.9 cm

59.4 x 84.1 cm

42 x 59.4 cm

29.7 x 42 cm

21 x 29.7 cm

14.85 x 21cm

10.5 x 14.85 cm

7.4 x 10.5 cm

5.2 x 7.4 cm

3.7 x 5.2 cm

2.6 x 3.7 cm

Size in inches

33.1 x 46.8 inches

23.4 x 33.1 inches

16.5 x 23.4 inches

11.7 x 16.5 inches

8.3 x 11.7 inches

5.8 x 8.3 inches

4.1 x 5.8 inches

2.9 x 4.1 inches

2.0 x 2.9 inches

1.5 x 2.0 inches

1.0 x 1.5 inches

Often used for

Technical drawings, posters.

Technical drawings, posters.

Technical drawings, posters.

Posters, presentations.

Standard printer paper.

Leaflets, diaries, books.

Postcards, photos.

Postcards, leaflets, stickers.

Business cards.


Tickets, stamps.


What size is A3 paper?


A3 paper measures 297 mm x 420 mm

A3 is two times the size of A4 which is the standard letter-sized paper. Some printers can also print on sheets of A3 paper which is the size of a small poster.

A3 is bigger than A4, A5, A6, A7, A8, A9 and A10 but half the size of A2.

What size is A4 paper?


A4 paper measures 210 mm x 297 mm

A4 is the standard letter paper size in the UK and is widely used in printers or copier machines. It’s often purchased in ‘paper reams’. It’s the most common paper size used across the world.

Before standardisation and adoption of the metric system, the UK’s most common paper size was ‘foolscap’, which measured 8 inches x 13 inches (203 mm x 330 mm).

A4 is bigger than, A5, A6, A7, A8, A9 and A10.


What size is A5 paper?


A5 paper measures 148.5 mm x 210 mm

A5 is one size smaller than A4 If you fold a landscape A4 sheet of paper in half across the middle (folded top to bottom), it would equal an A5-sized sheet of paper. A5 is the size often used for flyers or small notepads.

A5 is bigger than A6, A7, A8, A9 and A10.

What are the US Paper sizes?


There are 4 US paper sizes that are common to the USA and Canada, belonging to the North American paper class which follows the ANSI standard (American National Standards Institute) size. As the Imperial system is used, measurements are typically stated in inches.

There are also 3 additional less common paper sizes including government letter / legal and half letter sizes.

Standard paper sizes in the USA are Letter and Legal which measure 8.5 x 11 inches and 8.5 x 14 inches respectively.

US Paper Size Chart

Paper Class

Junior Legal




Half Letter

Government Letter

Government Legal

Size in inches

8 x 5 inches

8.5 x 11 inches

8.5 x 14 inches

11 x 17 inches

5.5 x 8.5 inches

8 x 10 inches

8.5 x 13 inches

Size in mm

203 x 127 mm

216 x 279 mm

216 x 356 mm

279 x 432 mm

140 x 216 mm

203 x 254 mm

216 x 330 mm

Size in cm

20.3 x 12.7 cm

21.6 x 27.9 cm

21.6 x 35.6 cm

27.9 x 43.2 cm

14 x 21.6 cm

2.03 x 25.4 cm

21.6 x 33 cm

Often used for

Writing pads.

Office, Academic.

Legal pads, contracts.

News papers.

Flyers, greetings cards.

Not commonly used.

Not commonly used.

Paper Size Questions & Answers

What size is standard Printer Paper?

Standard printer paper size in the USA is Letter – 8.5 x 14 inches (216 x 279 mm)

Standard printer paper size in the UK is A4 – 210 x 297 mm (8.3 x 11.7 inches)


Why do paper sizes differ in the USA and UK / internationally?

US and UK / international paper sizes that are most commonly used in their respective countries differ for the following reasons:

  • Different systems of measurement.
  • History & independence.
  • Design, mathematics & Industry.


Systems of measurement

The US uses the imperial system (inches) and the UK uses the metric system (millimetres and centimetres) to measure their paper sizes. Conversions of sizes between the two systems can give odd measurements.


History & Independence

After world war 2 much of Europe had to be rebuilt and a standardised measurement system (metric) was put in place to aid that rebuild. The USA was already very independent and since international trade wasn’t what it is today. There was no need for the US to adopt the same system, plus they also wanted to maintain their own independence.


Design & Mathematics & Industry

Original paper manufacture in the US was done by hand in moulds using measurements in inches in the standard letter size, whereas international paper formats were made using the mathematical ratio of 2 to 1, folding paper in half across its width gives exactly the next size of paper down.

As the imperial system was in place in the USA during the industrial revolution, machinery was manufactured using inches. Whilst internationally the metric system was used, whenever there were government debates in the US around switching to metric, this would have been problematic and the influence of big businesses meant switching was a none starter.

What is ISO & ANSI with regards to paper?

In the US the ANSI is the American National Standards Institute that set the standards for paper sizes in North America.

In the UK / internationally, paper sizes are set by the ISO (International Organisation for Standardisation ) under rule 216.

What is the Aspect Ratio of International ISO paper?

The aspect ratio of ISO paper is the square route of 2 or 1.4142:1

If you’re looking to purchase paper here in the UK, we sell a range of office paper for your printer, as well as ink and toner cartridges.